The court voted 6:3 to void the election on the ground that it failed to be held in a single day in accordance with the constitution.

On Feb. 2, voting was not held in 28 constituencies in eight southern provinces, where no candidates had been registered due to disruption from anti-government protesters.

The court ruled on a petition submitted by the Office of the Ombudsman, in which Kittipong Kamolthamwong, a law lecturer with Thammasat University, argued the election violated the constitution and asked it to be invalidated.

In a hearing on Wednesday, judges of the court heard testimony from representatives of the Office, caretaker government and the Election Commission (EC).

In the ruling, the court also asked the EC and the government to work out a new election date.

The main opposition Democrat Party, which had boycotted the Feb. 2 election, might not contest a new election, party spokesman Chavanond Intarakomalayasut said earlier.

EC member Somchai Srisuthiyakorn said on Thursday that whatever the ruling was, it would not be able to end the current political impasse.

The pro-government United Front for Democracy against Dictatorship, also known as "red shirt" movement, is expected to oppose the verdict, Somchai said, adding protesters would not make it easy for a new election to take place anytime soon.

Anti-government protest leader Suthep Thaugsuban has insisted on carrying out reform before election, saying protesters will try to make new election void too.